JP2007511985A - Priority-based arbitration for TDMA schedule implementation in multi-channel systems - Google Patents

Priority-based arbitration for TDMA schedule implementation in multi-channel systems Download PDF

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JP2007511985A
JP2007511985A JP2006541627A JP2006541627A JP2007511985A JP 2007511985 A JP2007511985 A JP 2007511985A JP 2006541627 A JP2006541627 A JP 2006541627A JP 2006541627 A JP2006541627 A JP 2006541627A JP 2007511985 A JP2007511985 A JP 2007511985A
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guardian
channel
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ザンステグ,フィリップ・ジェイ
ドリスコル,ケヴィン
ホール,ブレンダン
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ハネウェル・インターナショナル・インコーポレーテッド
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Priority to PCT/US2004/039249 priority patent/WO2005053243A2/en
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/28Data switching networks characterised by path configuration, e.g. local area networks [LAN], wide area networks [WAN]
    • H04L12/44Star or tree networks
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00Data switching networks
    • H04L12/28Data switching networks characterised by path configuration, e.g. local area networks [LAN], wide area networks [WAN]
    • H04L12/42Loop networks
    • H04L12/427Loop networks with decentralised control
    • H04L12/43Loop networks with decentralised control with synchronous transmission, e.g. time division multiplex [TDM], slotted rings

Abstract

  A multi-channel TDMA network with priority-based arbitration is provided. The network includes a plurality of channels and a plurality of nodes adapted to transmit and receive data. Through each channel, all nodes are coupled to communicate data with all other nodes. Within each channel, each node is assigned a unique priority rank. Only the node with the highest priority rank is allowed to transmit data during the time slot. For each channel of a multi-channel network, multiple nodes are ranked in different priority directions. Nodes are connected through at least two hubs, each hub associated with a guardian.

Description

This application is related to US Provisional Patent Application No. 60/523785, filed Nov. 19, 2003, entitled “PRIORITY BASED ARBITRATION FOR TDMA SCHEDULE ENFORCEMENT IN A DUAL LINK SYSTEM”. Priority Based Arbitration), US Provisional Application No. 60/560323, filed Apr. 6, 2004, entitled “MESSAGE AUTHENTICATION IN A COMMUNICATION NETWORK (Message Authentication in Communication Networks)”, November 19, 2003 US Provisional Patent Application No. 60 / 523,782, entitled “HUB WITH INDEPENDENT TIME SYN” HRONIZATION (hub with independent time synchronization) "and US Provisional Application No. 60/523833, filed November 19, 2003, titled" PARASITIC TIME SYNCHRONIZATION FOR A CENTRALIZED TDMA BASSED COMMUNICATION GARD All of these US provisional applications are hereby incorporated by reference in their entirety.

  This application is also related to the following co-pending patent applications filed concurrently with this application, all of which are incorporated herein by reference.

US Patent Application No. __ / ___ (Attorney Docket No. H0005281-1633, title “PARASITIC SYNCHRONIZATION FOR A CENTRALIZED TDMA BASED COMMUNICATIONS GUARDIAN” (parasitic time synchronization for centralized TDM-based communication guardian, 52 or below) Also called application;
US Patent Application No. __ / ____ (Attorney Docket No. H0007587-1633, titled “PORT DRIVEN AUTHENTICATION IN A NETWORK”, hereinafter also referred to as' 7587 application; and US Patent Application No. _______ (patent attorney serial number H0005031-1633, title “ASYNCHRONOUS HUB”), hereinafter also referred to as the '5031 application.

  The following description relates to the field of electronics and specifically to priority-based arbitration for TDMA-based communication protocols.

  Distributed fault tolerant communication systems are used, for example, in applications where a failure can possibly lead to injury or death of one or more people. Such an application is referred to herein as a “safety critical application”. One example of a safety critical application is a system used for monitoring and managing sensors and actuators included in the fields of automobiles, aircraft electronics, industrial control, and the like.

  The architecture considered for safety critical applications is generally a time-triggered architecture, in which nodes use synchronized time to coordinate access to common resources such as a communication bus. One of the architectures normally considered for use in such safety critical applications is the time triggered architecture (TTA). In a TTA system, multiple nodes communicate with each other via two replicated high-speed communication channels using a time-triggered protocol such as Time-Triggered Protocol / C (TTP / C).

  A fault that uses TDMA as a medium access strategy, where each node is allowed to periodically utilize the full transmission capacity of the bus for a fixed amount of time called a time division multiple access (TDMA) slot. Tolerant protocol (eg TTP / C). As long as each node uses only its statically allocated TDMA slots, a collision-free access to the bus can be ensured.

  Usually, transmission of messages by nodes in a TTP network is controlled by a schedule table that determines which nodes are allowed to transmit in each TDMA slot and also defines the start time and duration of the TDMA slot. This start time and duration defines the transmission window in which the node is allowed. The node's transmitter must start sending the message after the window starts and must finish before the window ends. A node that does not have permission to transmit listens for transmission until the duration has elapsed when the TDMA slot begins. The timing at which a node transmits and receives is controlled by the local clock of the node, which is synchronized to other nodes in the system by a distributed clock synchronization algorithm. In practice, complete synchronization of the clocks of all nodes is not possible, so that the clocks of each node are slightly skewed with respect to each other. As such, a transmitter at a node may begin sending a message before one or more of the receiving nodes are ready to listen. Similarly, one node may continue transmission after another node stops listening. In addition, a degraded node may attempt to transmit well outside the window assigned to it.

  Centralized guardians have been considered to limit the propagation of such faults. These guardians (or central guardians) ensure that a degraded node transmitter cannot broadcast to the network outside the window assigned to it. At the beginning of the TDMA slot, after a predefined delay, the guardian opens a window that allows the node to send a message to the network. If the node is operating correctly, it will begin sending immediately after the guardian window is opened and will complete sending before the window is closed. Ideally, the receiving node (i.e. the listening node) starts listening at the beginning of the TDMA slot until the guardian window is closed. The guardian blocks transmissions from the node that do not occur within the transmission window.

  One problem with the guardian's technical status is that the implementation of the guardian function duplicates the protocol logic engine implemented in the node because it has independent knowledge of the communication schedule and timing parameters such as slot order, transmission start time, etc. It is necessary. Implementation of the protocol logic engine within the guardian leads to a very complex guardian design. With the centralization of the guardian's role in network data flow, the guardian itself has become a critical architectural component. The complexity of guardian design is an important issue for design viability in safety critical applications. For example, in some cases, gate level failure analysis is required before using the guardian design for safety critical applications. In this case, the complexity of performing such guardian failure analysis has a significant financial impact on product development costs. In some applications, the guardian circuit may be required to perform a self test to verify its own health. The complexity of these self tests is also directly related to the complexity of the guardian.

  Another problem is that for some protocols, current guardian designs based on internally implemented protocol logic engines require the guardians in the network to be combined together. Embodiments of the present invention remove this requirement.

  This further introduced the possibility of failure in the form of consistency between the guardian and the nodes it protects. By requiring the guardian to maintain knowledge of the current state or past state in the form of transmission order, an implementation vulnerability to state updates remains, which is due to environmental factors such as high energy neutrons. May be introduced.

  There is a need in the art for a simplified guardian design for the reasons described above and other reasons discussed below, which will be apparent to those of ordinary skill in the art upon reading and understanding the specification.

  Embodiments of the present invention allow a simple priority based arbitration mechanism to be implemented within the central guardian of a TDMA based protocol communication network. Instead of implementing a full protocol engine with schedule knowledge within the guardian, embodiments of the present invention allow a central guardian to arbitrate between member nodes of the system attempting simultaneous communications on the network.

  In one embodiment, a multi-channel network with priority based arbitration is provided. The network includes a plurality of nodes adapted for each node to transmit and receive data, and a plurality of hubs, each hub having a communication link with the plurality of nodes. Each node is adapted to communicate with all other nodes via the one or more hubs, and the communication link between any one hub and the plurality of nodes is a first channel. Define The network further includes a plurality of guardians, each guardian is associated with one hub, and each node is adapted to transmit over a channel during a time slot. For each channel of the multi-channel network, each node is assigned a unique priority rank so that no two nodes on a channel have the same assigned priority rank. For each channel, the priority rank of each of the plurality of nodes is in a different direction. Which node in the time slot allows the first guardian of the plurality of guardians of the associated hub to allow only the winning node with the highest assigned priority rank to transmit over the channel. Decide if you are allowed to send to.

  In another embodiment, a network is provided. The network includes a plurality of sub-networks and a plurality of nodes adapted to transmit and receive data. Through each subnetwork, all nodes are coupled to communicate data with all other nodes. For each subnetwork, each node is assigned a unique priority rank. The winning node of the plurality of nodes is identified as having the highest priority rank for at least one subnetwork and is allowed to transmit during the time slot. For each channel, nodes are given ranks with different priority directions.

  In another embodiment, a method for priority-based arbitration of a central guardian of one channel of a TDMA multi-channel network is provided. The method assigns a unique priority rank to each node coupled to the one channel, and a first preamble indicating an intention of a first node of the plurality of nodes to transmit during a time slot Observing reception of a signal; and an intention of a second node of the plurality of nodes transmitting during the time slot within a predefined time interval from observing the reception of the first preamble signal. Observing reception of a second preamble signal shown. When the first node has a higher priority rank than the second node, the method further allows only the first node to transmit over the one channel during the time slot. Including the steps of: When the second node has a higher priority rank than the first node, the method further allows only the second node to transmit over the one channel during the time slot. Including the steps of: The unique priority rank direction is different for each channel of the multi-channel network.

  In another embodiment, a multi-channel network is provided. The network includes means for centralized guardian priority-based arbitration for a plurality of nodes. Means for assigning a unique priority rank to each of a plurality of nodes coupled to a first channel of the multi-channel network; and a time slot of a first node of the plurality of nodes. Means for observing reception of a first preamble signal indicating intent to transmit in, and a second of the plurality of nodes within a predefined time interval from observing the reception of the first preamble signal Means for observing the reception of a second preamble signal indicating the intention to transmit during the time slot of the node. Means for allowing only the first node to transmit during the time slot when the first node has a higher priority rank than the second node; and Means for allowing only the second node to transmit during the time slot when the first node has a higher priority rank than the first node. The unique priority rank direction is different for each channel of the multi-channel network.

  In another embodiment, a computer-readable medium having computer-executable instructions for performing a method of priority-based arbitration of a one-channel central guardian of a TDMA multi-channel network is provided. The method indicates assigning a unique priority rank to each node of a plurality of nodes coupled to the one channel and indicates the intent of a first node of the plurality of nodes transmitting during a time slot. Observing reception of a first preamble signal; a second of the plurality of nodes transmitting during the time slot within a predefined time interval from observing the reception of the first preamble signal; Observing receipt of a second preamble signal indicative of the intent of the node. When the first node has a higher wired rank than the second node, the method further allows only the first node to transmit over the first channel during the time slot. And when the second node has a higher wired rank than the first node, the method further includes that only the second node is on the first channel during the time slot. Allowing the transmission. The unique priority rank direction is different for each channel of the multi-channel network.

  The invention can be more readily understood and further benefits and uses of the invention will become more readily apparent when considered in view of the description of the preferred embodiments and the accompanying drawings.

  In accordance with common practice, the various described features are not shown to scale but are drawn to emphasize features relevant to the present invention. Reference numbers indicate similar elements throughout the figures and text.

  In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and other embodiments can be utilized, and logical, mechanical, and electrical changes can be made to the spirit of the invention. It should be understood that additions can be made without departing from the scope and scope. The following detailed description is, therefore, not to be construed in a limiting sense.

  Embodiments of the present invention allow a simple priority based arbitration mechanism to be implemented within the central guardian of a TDMA based protocol communication network. Instead of a full protocol engine in the guardian, embodiments of the present invention allow the central guardian to arbitrate access to the communication channel between member nodes that each already implements the full protocol engine on its own. enable. Embodiments of the present invention do not require the central guardian to know the underlying protocol as to which nodes are allowed to transmit during which TDMA slots. However, for a single fault tolerant network design, the availability of network communications achieved using the present invention is comparable to the availability of guardians performing full protocol implementations. By not requiring specific knowledge of protocol behavior, the present invention allows the implementation of very simple synchronization logic.

  The present invention differs from previous systems in that it prevents data collisions caused by two nodes transmitting simultaneously on one channel without duplicating the node's protocol logic engine within the guardian. This has benefits for current practices, including a much less complex implementation and simplified guardian failure analysis for safety critical domains, and removes guardian dependencies on protocol state logic and signals.

  The presented invention takes advantage of the fact that in many networks, channels are often replicated to ensure continued availability and fault tolerance of data communications. By utilizing the nature of the multi-channel network, it is possible to ease the requirements of the guardian implementation judgment regarding the guardian of the current technical state of the art. Rather than guaranteeing that only the correct node can transmit data on a channel during a TDMA slot, embodiments of the present invention are: 1) only one node is allowed to transmit data on a given channel; 2) Ensure that the correct node (ie, the node that is allowed to transmit during the TDMA slot according to the protocol) has exclusive access to at least one channel to transmit its data. Such a philosophy is consistent with the assumptions underlying such protocols because the purpose of the replicated channels in these applications is only availability assurance. By using such a design principle, a centralized guardian implementation can be realized based on a simple priority-based arbitration circuit.

  FIG. 1 is a block diagram of one embodiment of a multi-channel network, indicated generally at 100, in accordance with the teachings of the present invention. Although a dual channel network is illustrated in FIG. 1 for the sake of simplicity, those skilled in the art will readily apply embodiments of the present invention to networks having more than two channels after reading this specification. You will immediately understand what will be done. The network 100 includes a plurality of nodes 102-1 to 102-N. In this embodiment, network 100 includes a plurality of nodes 102-1 to 102-N, each coupled to hubs 104-1 and 104-2. In one embodiment, data is transmitted in a frame from one node 102-1 to 102-N to another node in network 100 via hubs 104-1 and 104-2. In one embodiment, each subnetwork that includes a communication link between an individual hub and a plurality of nodes 102-1 to 102-N defines a single network channel. In one embodiment, the network 100 operates as a dual channel system, where the hub 104-1 operates to distribute data communications on the “0” channel between the nodes 102-1 to 102-N. The hub 104-2 then operates to distribute data communications on the “1” channel between the nodes 102-1 to 102-N. In one embodiment, one or more electronic devices 106-1 to 106-P are connected to nodes 102-1 to 102-N. In one embodiment, electronic devices 106-1 through 106-P include sensors, processors, actuators, controllers, input devices, and the like that communicate data frames over network 100.

  The network 100 operates on a time division multiple access (TDMA) based communication protocol, where each node 102-1 to 102-N is assigned a transmit TDMA slot order. In such a network, each node implements the protocol independently and has complete knowledge of the current protocol state (ie, each node determines which TDMA slot is the current TDMA slot, current TDMA slot The time when the transmission window of the slot is opened, the time when the transmission window of the current TDMA slot is closed, whether the node has permission to transmit during the transmission window of the current TDMA slot, and which TDMA slot is the next TDMA slot And knows independently whether it is a future TDMA slot).

  Each of hubs 104-1 and 104-2 includes a central guardian 103-1 and 103-2, which are nodes 102-1 through 102- through each associated channel. Functions to coordinate the propagation of data communications from N. In order to reduce the complexity of the guardian 103-1 and 103-2 functions, the present invention provides a simple priority-based arbitration protocol.

  Priority-based arbitration of the network 100 is achieved as follows. In one embodiment, during operation, each node 102-1 through 102-N is designated a first priority scheme on channel 0 and a second priority scheme on channel 1. For example, in one embodiment, nodes 102-1 through 102-N have an associated priority increasing from 1 to N on channel 0. On channel 1, the priorities are reversed, so that nodes 102-1 to 102-N have associated priorities decreasing from N to 1. For each associated channel, guardians 103-1 and 103-2 only allow propagation through the hubs 104-1 and 104-2 of data transmitted by the highest priority node attempting transmission during a time slot. . Ideally, each node 102-1 to 102-N has completely accurate knowledge of whether transmission is allowed during the current TDMA slot and only one node 102-1 to 102-N. Attempts to transmit data over the channel during a single TDMA slot. Under this condition, the guardians 103-1 and 103-2 play a passive role because no arbitration for the channel transmission right is required. However, under a single failure scenario, a degraded node among the nodes 102-1 to 102-N attempts an unauthorized transmission during a TDMA slot assigned to another node 102-1 to 102-N. There is. Under the priority scheme of one embodiment of the present invention, if node 102-1 (for example) attempts to transmit during the time slot of 102-3, node 102-1 (priority of 1 on channel 0) Have a higher priority than node 102-3 (which has a priority of 3 on channel 0). Therefore, the guardian 103-1 selects the node 102-1 as the “winning” node of this arbitration contest. Guardian 103-1 has access to node 102-3 to transmit data over channel 0 because node 102-3 always loses priority arbitration competition with node 102-1 on this channel. (Even if the node 102-3 is allowed to transmit by the protocol). However, in channel 1, node 102-3 always wins the priority arbitration competition with node 102-1. Therefore, the guardian 103-2 refuses to access the node 102-1 for transmitting data via the channel 1, and permits the access to the node 102-3. As a result, the node 102-3 can always transmit data over at least one channel during the TDMA slot assigned to it.

  Under a single failure assumption for a network of at least two channels with different priority directions, embodiments of the present invention ensure that good transmission is obtained on at least one channel (ie assigned to it). The node that transmits correctly during the TDMA slot is selected as the winning node on at least one channel). In one embodiment, each TDMA slot is arbitrated without history using only the information sensed during a particular arbitration period. In other embodiments, a guardian of a channel incorporates history information into the arbitration decision to determine which of a plurality of competing nodes is the correct node allowed to transmit on the channel. One can try (eg, use history to remove a node as a competitor based on the history of which node recently sent).

  FIG. 2 is a block diagram of one embodiment of a multiple hub-based network, indicated generally at 200, in accordance with the teachings of the present invention. In this embodiment, the network 200 includes a plurality of nodes 202-1 to 202-N each coupled to a plurality of hubs 204-1 to 204-H. In one embodiment, each subnetwork that includes a communication link between an individual hub and a plurality of nodes 202-1 to 202-N defines a single network channel. The priority-based arbitration in the network 200 operates on the same basis as the dual hub network 100 described in the embodiment of FIG.

  Data is transmitted in frames via hubs 204-1 through 204-H from one node 202-1 through 202-N in network 200 to another node. As described with respect to the network 100 of FIG. 1, in one embodiment, the network 200 operates in a time division multiple access (TDMA) based communication protocol, where each node 202-1 through 202-N has an in-channel Transmission slot order (ie, TDMA slots) is assigned. In one embodiment, the network is a TTP network and the TDMA slot is an SRU slot. Each of hubs 204-1 through 204-H includes a central guardian 203-1 through 203-H that implements the priority-based arbitration of the present invention, and guardian 203-1 through 203-H includes node 202-1. To 202-N have different priority directions. In one embodiment, under a single failure assumption, an embodiment of the present invention is that a good node transmission can be performed in the network 200 as long as at least one channel has a guardian that utilizes a different priority direction than the other channels. Ensure that it is obtained on at least one channel. In another embodiment, each of the guardians 203-1 through 203-H uses a different priority scheme for the nodes 202-1 through 202-N. In one embodiment, guardians 203-1 through 203-H are adapted to have a memory that holds a priority scheme in a table. In one embodiment, the guardian 203-1 through 203-H memory can be reprogrammed using a different priority scheme. In another embodiment, the priority of nodes 202-1 through 202-N is determined by which port of each hub 204-1 through 204-H is wired to each node.

  FIG. 3 is a diagram of one embodiment of a priority-based arbitration timing diagram for a network such as network 200 described with respect to FIG. FIG. 3 includes one or more preamble signals 320 received from nodes 202-1 to 202-N by a one-channel guardian 203 of network 200. FIG. The preamble signal received from the node indicates that the node that transmitted the preamble signal intends to transmit data during the current TDMA slot 355. In one embodiment, nodes 202-1 through 202-N transmit preamble signal 320 to guardian 203 over the same communication link (such as communication link 210) used to transmit and receive data communications. In one embodiment, nodes 202-1 through 202-N transmit preamble signals to guardian 320 over a separate communication link (not shown) utilized for transmitting and receiving data communications.

  At the beginning of the current TDMA slot 350, the guardian 203 opens an arbitration window 330 of time π in duration. The finite time interval π represents the maximum timing synchronization skew of the nodes 202-1 to 202-N that is expected to have a correctly operating node 202-1 to 202-N. In some embodiments, the arbitration window 330 has a duration of π plus a signal propagation delay constant. The guardian 203 waits for the first preamble signal 325. If only one preamble signal is received during the arbitration window 330, no arbitration between the nodes is necessary, and the guardian 203 closes the arbitration window 330 and transmits the transmission window for the node that transmitted the one preamble signal. Open 340. This allows the node to send data to other nodes over the channel. In one embodiment, the send window 340 is opened after a predefined time delay after the arbitration window 330 is closed. Since each node 202-1 through 202-N knows that it is assigned a TDMA slot that is exclusively allowed to transmit (by protocol), in a properly operating network, a single preamble signal Only 325 is received by the guardian 203 during the arbitration window 330. However, under a single failure assumption, a failed node may attempt to transmit during another node's TDMA slot. In that case, the guardian 203 receives two preamble signals (325 and 326) from two different nodes during the arbitration window 330. The guardian 203 selects which of these two nodes is allowed to transmit across the channel in the TDMA slot 350. In one embodiment, the guardian 203 arbitrates between the two nodes, allowing only the node with the highest priority assignment to transmit over the channel. In order to make this arbitration decision, the guardian 203 does not need knowledge of which nodes must be allowed to transmit according to the underlying protocol. At the start of the next TDMA slot, the guardian 203 opens a transmission window 340 for the node with the highest priority assignment.

  In order to perform priority-based arbitration, in one embodiment, the guardians 203-1 through 203-H may use the time bases of nodes 202-1 through 202-N to coordinate opening and closing the transmission window. As a result, guardians 203-1 through 203-H and nodes 202-1 through 202-N come to agree on the timing of the TDMA slots. In one embodiment, the TDMA slot lengths of the different nodes are different, corresponding to the ratio of total bandwidth allocated to individual member nodes, each TDMA slot allowing a certain amount of data transmission. In one embodiment, for each channel in network 200, the associated guardians 203-1 to 203-H, as shown in the '5281 application previously referenced and incorporated herein by reference, It is synchronized with the network 200 via beacons transmitted by the nodes 202-1 to 202-N. In one embodiment, network 200 is a TTP network and the beacons transmitted by nodes 202-1 through 202-N are action time signals. Further details regarding the synchronization of guardians 203-1 to 203-H with nodes 202-1 to 202-N are described in the '5281 application, which is incorporated herein by reference. In another embodiment, the guardian can open an arbitration window based on the arrival of the first preamble signal rather than based on the beginning of the TDMA slot indicated via the beacon transmitted by the node. In another embodiment, the arbitration window is closed upon receipt of the second preamble signal and the arbitration winner is determined immediately.

  FIG. 4 is a block diagram of another embodiment of a multi-hub network, indicated generally at 400, in accordance with the teachings of the present invention. A plurality of hubs 404-1 through 404 -X are coupled to nodes 402-1 through 402 -T, respectively. A plurality of hubs 414-1 to 414-X are coupled to nodes 412-1 to 412-R, respectively. Each hub 404-1 to 414-X is coupled to one hub 414-1 to 414-X via an associated communication link 425-1 to 425-X to create a linked hub pair. The sub-network that includes each linked hub pair and the communication link that couples them to nodes 402-1 through 402-T and 412-1 through 412-R defines a single communication channel. Each node 402-1 through 402-T and 412-1 through 412-R communicates with all other nodes 402-1 through 402-T and 412-1 through 412-R via linked hubs. be able to. Each of hubs 404-1 through 404 -X and 414-1 through 414 -X uses priority-based arbitration to communicate data over each associated channel and data over communication links 425-1 through 425-X. Includes central guardians 403-1 through 403-X and 413-1 through 403-X that function to coordinate the propagation of communications.

  Priority-based arbitration for the network 400 is achieved as follows. In one embodiment, in operation, each node 402-1 through 402-T and 412-1 through 412-R is assigned a priority based on the global priority scheme of each channel. For example, in one embodiment, nodes 402-1 through 402-T and 412-1 through 412-R have increasing associated global priorities on channel 0 from 1 to T + R. On channel 1, the priorities are reversed so that nodes 402-1 through 402-T and 412-1 through 412-R have associated priorities decreasing from T + R to one. Ideally, each node 402-1 to 402-T and 412-1 to 412-R has fully accurate knowledge of whether transmission is allowed during the current TDMA slot and one node Only 402-1 through 402-T and 412-1 through 412-R attempt to transmit data over the channel during a single TDMA slot. Under this condition, the guardians 403-1 to 403-X and 413-1 to 413-X play a passive role because no arbitration regarding the channel transmission right is required. However, under a single failure scenario, one of the nodes 402-1 through 402-T and 412-1 through 412-R that has deteriorated is another node 402-1 through 402-T and 412-1 through 412. -Unauthorized transmission may be attempted during the TDMA slot assigned to -R. As described with respect to FIG. 2, priority-based arbitration allows only the node with the highest priority to transmit on the channel. One result of the global priority scheme of the above embodiment is that any of the nodes 402-1 through 402-T (indicating intent to transmit on channel 0) that transmit the preamble signal to the hub 404-1 is The node 412-1 has a higher priority than any of the nodes 412-1 to 412-R indicating the intention of the transmission to 414-1. Thus, any of the nodes 412-1 to 412-R (indicating intent to transmit on channel 1) that transmit the preamble signal to the hub 414-2 is the node 402-1 that indicates intent to transmit to the hub 404-2. To 402-T has a higher priority.

  On channel 0, the guardian 403-1 either 1) receives a preamble signal from a single node 402-1 to 402-T, or 2) two of the nodes 402-1 to 402-T transmit a preamble signal The hub 404-1 transmits data to the hub 414-1 over the communication link 425-1 when either of the arbitrating the winning node (ie, the node having the highest priority) is performed. Allow that. As a result, the guardian 413-1 transmits all of the nodes 412-1 to 412-R on channel 0 because all of the nodes of the hub 414-1 have a lower priority than any of the nodes of the hub 404-1. To block. In contrast, guardian 413-1 either 1) receives a preamble signal from a single node 412-1 to 412-R, or 2) two of nodes 412-1 to 412-R transmit a preamble signal. The hub 414-1 is only when the guardian 403-1 has not received the preamble signal from any of the nodes 402-1 through 402-T when arbitrating the winning node after The node is allowed to send data to hub 404-1 over communication link 425-1. If the guardian 403-1 has not received a preamble signal from a higher priority node, the guardian 403-1 will have any of the nodes 412-1 to 412-R on channel 0 during its time slot. Block sending.

  The channel 1 global priority scheme is opposite in direction to channel 0, so in channel 1 the guardian 413-2 either 1) receives a preamble signal from a single node 412-1 to 412-R or 2) When one of the nodes 412-1 to 412-R arbitrates the winning node (ie, the node with the highest priority) after transmitting the preamble signal, the hub 414-2 Permits transmission of data to hub 404-2 via communication link 425-2. As a result, all of the nodes of hub 404-2 have lower priority than any of hub 414-2, so that all of nodes 402-2 through 402-T are on channel 1. Block sending. In contrast, the guardian 403-2 either 1) receives a preamble signal from a single node 402-1 to 402-T or 2) two of the nodes 402-1 to 402-T transmit a preamble signal The hub 404-2 will only receive the preamble from any of the nodes 402-1 through 402-T when arbitrating the winning node after Allows the node to send data to hub 414-2 via communication link 425-2. If the guardian 413-2 has not received a preamble signal from a higher priority node, the guardian 413-2 will have any of the nodes 412-1 to 412-T on channel 1 during its time slot. Block sending.

  As previously mentioned, under a single failure assumption in a network 400 of at least two channels with different priority directions, embodiments of the present invention allow nodes that are allowed to transmit by the underlying protocol to Ensure that transmission is achieved on at least one channel.

  FIGS. 5a and 5b are example embodiments of a channel 0 priority-based arbitration timing diagram for a network such as network 400 described with respect to FIG. 4, including the global priority scheme described for channel 0 with respect to FIG.

  In one embodiment, communication links 425-1 through 425-N are full duplex to allow bi-directional communication between coupled hub pairs with the priority-based arbitration timing 500 shown in FIG. 5a. It is a communication link. Arbitration window 530 is opened for guardian 403-1 upon detection of the beginning of a TDMA slot (shown at 550). In one embodiment, the arbitration time window 530 has a duration of π. The finite time interval π represents the maximum timing synchronization skew of nodes 402-1 to 402-T that is expected to have nodes 402-1 to 402-T operating correctly. In some embodiments, the arbitration window 530 has a duration of π plus a signal propagation delay constant. Guardian 403-1 arbitrates among all nodes 402-1 through 402-T that have transmitted a preamble signal (such as preamble signals 525 and 526) during arbitration time window 530. When guardian 403-1 arbitrates the winning node, it allows that node to send data for transmission to hub 414-1 after arbitration time window 530 is closed (shown at 532). Next, guardian 413-1 blocks nodes 412-1 to 412-R transmitting during TDMA slot 555 while opening transmission window 540 for the node that guardian 403-1 has won. .

  Arbitration window 535 is opened for guardian 413-1 upon detection of the start of a TDMA slot (shown at 550). The guardian 413-1 receives the preamble signal (preamble signals 527 and 528) during the arbitration time window 535 among the nodes 412-1 to 412-R in addition to the winning node from the arbitration of the nodes 402-1 to 402-T. Arbitration between all nodes that sent If the guardian 413-1 arbitrates the winning node from the nodes 412-1 to 412-R and does not receive a data transmission from the guardian 403-1 during the arbitration time window 535, the guardian 413-1 receives the arbitration time window. After 535 is closed (shown at 537), the winning node is allowed to send data to hub 404-1. Next, guardian 403-1 blocks nodes 402-1 through 402-T transmitting during its TDMA slot while guardian 413-1 opens transmission window 545 for the winning node. Arbitration window 535 must be longer than arbitration window 530 in duration. This is because the guardian 403-1 cannot make an arbitration decision until the arbitration window 530 is closed, and the guardian 413-1 makes an arbitration decision before making its own arbitration decision. This is because the guardian 403-1 must be given enough time to communicate. In one embodiment, arbitration window 535 has a duration of 2π.

  When the guardian 403-1 arbitrates the winning node, the guardian 403-1 opens the transmission window 540 so that the node can communicate with other channels via the hubs 404-1, 414-1 and the communication link 425-1. To send to other nodes. Meanwhile, guardian 413-1 blocks nodes 412-1 to 412-R from transmitting on the channel. If the guardian 403-1 does not arbitrate the winning node, after the arbitration window 530 closes, the guardian 413-1 opens the transmission window 545 for the one node 412-1 to 412-R having the highest priority. Knows that it is safe to open and allows the node to transmit from node 402-1 to 402-T via communication link 225-1.

  In order to make these arbitration decisions, the guardians 403-1 and 413-1 do not need knowledge of which nodes must be allowed to transmit according to the underlying protocol. In one embodiment, the priority-based arbitration timing for channel 1 of network 400 is such that the global priorities are reversed so that nodes 402-1 through 402-T and 412-1 through 412-R go from T + R to 1. Operates in the same manner as described in FIG. 5 except that it has a decreasing associated priority. In that case, the guardian 403-2 must listen to the preamble signals from the nodes 402-1 to 402-T and the hub 414-2, so that the guardian 403-2 can receive from the guardian 413-2. In order to allow propagation of arbitration decisions, it must keep its arbitration window open for a longer duration. Embodiments of the present invention ensure that node transmission is obtained on at least one channel of the network 400 as long as each channel has a guardian pair that utilizes a different global priority direction than the other channels.

  In one embodiment, communication links 425-1 through 425-N are half-duplex communication links (one direction at a time between coupled hub pairs) using the priority-based arbitration timing 510 shown in FIG. 5b. Only communication). In one embodiment, link 425-1 is half duplex with a default configuration that only allows communication from 404-1 (high priority hub) to 404-1 (low priority hub). Since the communication link 425-1 is half duplex, the guardian 403-1 must arbitrate blindly with respect to the guardian 413-1. Arbitration window 560 is opened for guardian 403-1 upon detection of the start of a TDMA slot (shown at 590). Guardian 403-1 arbitrates between all of nodes 402-1 through 402-T that transmit preamble signals (such as preamble signals 575 and 576) during an arbitration time window 560 of duration π. When guardian 403-1 arbitrates the winning node, it allows the winning node to transmit to hub 414-1 after arbitration time window 560 is closed (shown at 562). Meanwhile, an arbitration window 565 is opened for the guardian 413-1 upon detection of the beginning of a TDMA slot (shown at 590). Guardian 413-1 sends a preamble signal (such as preamble signals 577 and 578) during arbitration time window 565 in addition to notification from hub 404-1 about the winning node resulting from arbitration of nodes 402-1 to 402-T. Arbitrate between all transmitting nodes 412-1 to 412-R. Arbitration window 565 must be longer than arbitration window 560 in duration. This is because the guardian 403-1 cannot make an arbitration decision until the arbitration window 560 is closed, and the guardian 414-1 makes an arbitration decision before making its own arbitration decision. This is because the guardian 403-1 must be given enough time to communicate. In one embodiment, arbitration window 565 has a duration of 2π. If the guardian 403-1 arbitrates the winning node, the guardian 403-1 opens the transmit window 580 so that the node can connect the hubs 404-1, 414-1 and communication link 425-1 during the TDMA slot 595. Allow transmission to other nodes on the channel. Meanwhile, guardian 413-1 blocks nodes 412-1 to 412-R from transmitting on the channel. If guardian 403-1 does not arbitrate the winning node, after arbitration window 565 closes, guardian 403-1 declares hub 414-1 as the default winner. The guardian 413-1 then knows that it is safe to open the transmit window 585 for the highest priority nodes 412-1 to 412-R, and that node is in communication link 225 during the TDMA slot 595. -1 to allow transmission from node 402-1 to 402-T.

  FIG. 6 is a block diagram of an alternative form of network, indicated generally at 600, in accordance with the teachings of the present invention. Node 600 includes a hub and bus configuration. Each of hubs 604-1 through 604-N is directly coupled to nodes 602-1 through 602-P. Each of nodes 612-1 through 612-D is coupled to buses 625-1 and 625-2. Buses 625-1 and 625-2 are coupled to hubs 604-1 and 604-2, respectively. In operation, each node 602-1 through 602-P and 612-1 through 612-D transmits one frame on each of the N channels during all TDMA rounds. In one embodiment, the priority arbitration scheme provided throughout this specification includes nodes 602-1 and 602-P (ie, nodes directly coupled to hubs 604-1 to 604-N) and an N-channel bus. Applicable to arbitration between 625-1 and 625-2, where each bus is treated as a single node for priority arbitration purposes.

  FIG. 7 is a flowchart of one method of priority-based arbitration for a single-channel central guardian of a TDMA multi-channel network, indicated generally at 700. The method includes first assigning (710) a unique priority rank to each node coupled to the channel, where the unique priority rank direction for a node of a channel is determined by the multi-channel network. Different from the unique priority rank direction of another channel node. The method includes a first preamble signal reception indication (720) indicating a first node's intent to transmit during a time slot and a time within a predefined time interval from the first preamble signal reception observation. Proceed to observing (730) reception of a second preamble signal indicating the intention of the second node to transmit during the slot. When the first node has a higher priority rank than the second node, the method continues to allow only the first node to transmit over one channel during the time slot (740). ). When the second node has a higher priority rank than the first node, the method continues to allow only the second node to transmit over one channel during the time slot (750). ).

  By removing the requirement to store schedule information within the hub, the following benefits are achieved:

  a. Removal of tool issues related to central guardian schedule table development and verification of central guardian schedule correctness.

  b. Central Guardian complexity reduction by freeing the central guardian from the need to store and use central guardian schedule table information.

  c. Reduced sensitivity to hub state space and single event upset (SEU). In one embodiment, the single event upset is based on an upset induced by high energy neutrons. Embodiments of the present invention reduce SEU by not having the necessary schedule location related state to be stored by the guardian. Therefore, there is no state to be upset.

d. Removal of semantic dependency on guardian protocol status signals-Allows central guardian to be implemented across TDMA protocol mode changes resulting in different transmission orders without hub processing mode change signals-Without hub following schedule position Enabling Nodes Multiplexed in a Shared TDMA Slot In one embodiment, a simple heuristic is added to further increase the elasticity of the above-mentioned system guardian. In one embodiment, if a node shows activity before its time slot, it can be disabled from participating in arbitration. This effectively includes a node that transmits an incorrect preamble signal or all nodes that are not synchronized to the network. In another embodiment, if a node wins arbitration, the node can be blocked for one or more slots and not arbitrated.

  In one embodiment, the centralized guardian of the present invention is further derived from the port number to which the origin node is coupled, as shown in detail in the '7587 application incorporated herein by reference. The identifier is used to adapt the message sent via the associated hub. Thus, a node that receives two different messages simultaneously on separate channels can identify the two nodes sending the message, and in one embodiment, only messages from the granting node that are allowed to transmit during the TDMA slot by protocol. You can choose to accept. Further details regarding port-driven authentication in the network described above are in the '7587 application.

  Several forms are possible that implement the central guardian element of the present invention. This includes, but is not limited to, digital computer systems, programmable controllers, or field programmable gate arrays. Accordingly, another embodiment of the invention is a program instruction residing on a computer readable medium that, when implemented by such a controller, allows the controller to implement an embodiment of the invention. Computer readable media include all forms of computer memory including, but not limited to, magnetic disks, magnetic tape, CD-ROM, DVD-ROM, any optical data storage system, flash ROM, non-volatile ROM, or RAM. included.

  A number of embodiments of the invention have been described. Although particular embodiments have been illustrated and described herein, one of ordinary skill in the art will understand that all arrangements calculated to achieve the same purpose can replace the particular embodiments shown. I will. It should be understood that various changes to the described embodiments can be made without departing from the scope of the claimed invention. This specification is intended to cover all adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.

1 is a block diagram illustrating a dual channel network according to an embodiment of the present invention. 1 is a block diagram illustrating a multi-channel network according to an embodiment of the present invention. It is an arbitration timing diagram showing an embodiment of the present invention. FIG. 2 is a block diagram illustrating another multi-channel network according to an embodiment of the present invention. It is an arbitration timing diagram showing another embodiment of the present invention. It is an arbitration timing diagram showing another embodiment of the present invention. FIG. 2 is a block diagram illustrating another multi-channel network according to an embodiment of the present invention. 3 is a flowchart illustrating a method according to an embodiment of the present invention.

Claims (10)

  1. A plurality of nodes (202-1 to 202-N), each of the plurality of nodes (202-1 to 202-N) adapted to transmit and receive data;
    Each hub has a communication link with the plurality of nodes (202-1 to 202-N), and the communication link between any one hub and the plurality of nodes (202-1 to 202-N). A plurality of hubs (204-1 to 204-H) defining a first channel of the multi-channel network (200);
    Including
    Each node is adapted to communicate with all other nodes of the plurality of nodes (202-1 to 202-N) via the plurality of hubs (204-1 to 204-H);
    A plurality of guardians (203-1 to 203-H), each guardian associated with one of the plurality of hubs (204-1 to 204-H);
    Each node is adapted to transmit during a timeslot;
    Each node is assigned a unique priority rank to the channels of the multi-channel network (200);
    For each channel of the multi-channel network (200), the unique priority rank of each of the plurality of nodes (202-1 to 202-N) is in a different direction;
    The first guardian of the plurality of guardians (203-1 to 203-H) allows only the winning node with the highest assigned priority rank to transmit over the channel; Determining whether any of a plurality of nodes (202-1 to 202-N) is allowed to transmit data during the associated time slot;
    Network (200) with priority-based arbitration.
  2.   The network of claim 1, wherein the multi-channel network (200) is a TDMA network and the time slot is a TDMA slot.
  3. Each node of the plurality of nodes (202-1 to 202-N) transmits a preamble signal to the plurality of guardians to indicate the intention of transmission,
    The first guardian is adapted to observe receipt of a first preamble signal (325) from a first one of the plurality of nodes (202-1 to 202-N);
    When the first guardian observes reception of a second preamble signal (326) from a second of the plurality of nodes (202-1 to 202-N) within a predefined time interval; , Allowing the first guardian to transmit over the associated channel only one of the first node or the second node, wherein the first guardian is the first node Allows the first node to transmit when the node has a higher priority rank than the second node, and the first guardian allows the second node to have a higher priority than the first node. Allow the second node to transmit if it has a rank;
    When the first guardian does not observe the reception of the second preamble signal (326) within the predefined time interval, the first guardian passes through the channel with which the first node is associated. Allow to send,
    The network according to claim 1.
  4. Each guardian
    A memory in which a unique priority ranking of each node of the plurality of nodes (202-1 to 202-N) is stored in a memory;
    The memory is reprogrammable to change the unique priority ranking of each node of the plurality of nodes (202-1 to 202-N).
    The network according to claim 1.
  5. Each hub further includes a plurality of nodes, wherein each node of the plurality of nodes (202-1 to 202-N) is coupled to each hub of the plurality of hubs (204-1 to 204-H) via a port. Including
    A unique priority ranking of each node of the plurality of nodes (202-1 to 202-N) is determined by which port of the plurality it is coupled to;
    The network according to claim 1.
  6. The nodes of the plurality of nodes (202-1 to 202-N) and the plurality of guardians (203-1 to 203-H) are adapted to implement port-driven authentication;
    When the nodes of the plurality of nodes (202-1 to 202-N) receive different data on separate channels, the nodes of the plurality of nodes (202-1 to 202-N) Only accept data,
    The permitted node is a node that is permitted to transmit during the time slot by a protocol among the plurality of nodes (202-1 to 202-N).
    The network according to claim 1.
  7. Assigning a unique priority rank to each of a plurality of nodes (202-1 to 202-N) coupled to the one channel;
    Observing reception of a first preamble signal (325) indicating the intent of a first node of the plurality of nodes (202-1 to 202-N) to transmit during a time slot (355);
    Of the plurality of nodes (202-1 to 202-N) transmitting during the time slot (355) within a predefined time interval from observation of the reception of the first preamble signal (325). Observing reception of a second preamble signal (326) indicating the intent of the two nodes;
    Allowing only the first node to transmit over the one channel during the time slot (355) when the first node has a higher priority rank than the second node; ,
    Allowing only the second node to transmit over the one channel during the time slot (355) when the second node has a higher priority rank than the first node; ,
    And the unique priority rank direction is different for each channel of the multi-channel network (200).
    A method of priority-based arbitration of the central guardian of one channel of a TDMA multi-channel network (200).
  8. Multiple sub-networks,
    Adapted to send and receive data, and through each subnetwork, all nodes communicate with all other nodes (402-1 to 402-T and 412-1 to 412-R) A plurality of nodes (402-1 to 402-T and 412-1 to 412-R) coupled to
    Including
    For each subnetwork, each node is assigned a unique priority rank,
    A winning node of the plurality of nodes (402-1 to 402-T and 412-1 to 412-R) is identified as having the highest priority rank for at least one subnetwork and is in a time slot Is allowed to send to
    For each subnetwork, the plurality of nodes (402-1 to 402-T and 412-1 to 412-R) are ranked in different priority directions.
    network.
  9. The first subnetwork of the plurality of subnetworks further includes:
    Each node of the plurality of nodes (402-1 to 402-T and 412-1 to 412-R) is connected to one or more hubs (404-1 to 404-X and 414-1 to 414-X). One or more hubs coupled to at least one of the hubs and wherein one or more hubs (404-1 to 404-X and 414-1 to 414-X) are adapted to communicate with each other The network of claim 8, comprising (404-1 to 404-X and 414-1 to 414-X).
  10. Each subnetwork of the plurality of subnetworks is
    Each guardian of one or more guardians (403-1 to 403-X and 413-1 to 413-X) is connected to the one or more hubs (404-1 to 404-X and 414-1 to 414-41). X) and one or more guardians (403-1 to 403-X and 413-1 to 413-X) are associated with the plurality of nodes (402-1 to 402-T and One or more guardians (403) that allow only the one winning node with the highest priority rank of 412-1 to 412-R) to transmit over the sub-network during the time slot. -1 to 403-X and 413-1 to 413-X),
    Each node of the plurality of nodes (402-1 to 402-T and 412-1 to 412-R) transmits a preamble signal when intended to transmit,
    Each guardian of the one or more guardians (403-1 to 403-X and 413-1 to 413-X) is adapted to observe the reception of the first preamble signal (525) from the first node. And
    A first guardian of the one or more guardians (403-1 to 403-X and 413-1 to 413-X) is configured to receive a second preamble from a second node (528) within a predefined time interval. When observing the reception of the signal (526), the first guardian allows only one of the first node or the second node to transmit over the associated sub-network, and The first guardian allows the first node to transmit if the first node has a higher priority rank than the second node, and the first guardian Allowing the second node to transmit if the node has a higher priority rank than the first node;
    When the first guardian does not observe the reception of the second preamble signal (528) within the predefined time interval, the first guardian passes through the channel with which the first node is associated. Allow to send,
    The network according to claim 9.
JP2006541627A 2003-11-19 2004-11-19 Priority-based arbitration for TDMA schedule implementation in multi-channel systems Granted JP2007511985A (en)

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US52378203P true 2003-11-19 2003-11-19
US56032304P true 2004-04-06 2004-04-06
PCT/US2004/039249 WO2005053243A2 (en) 2003-11-19 2004-11-19 Priority based arbitration for tdma schedule enforcement in a multi-channel system in star configuration

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US20050129055A1 (en) 2005-06-16

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